rules_pip: update to new version

rules_pip has a new version [1] of their rule system, incompatible with the
version we used, that fixes a bunch of issues, notably:
 - explicit tagging of repositories for PY2/PY3/PY23 support
 - removal of dependency on host pip (in exchange for having to vendor
   wheels)
 - higher quality tooling for locking

We update to the newer version of pip_rules, rename the external
repository to pydeps and move requirements.txt, the lockfile and the
newly vendored wheels to third_party/, where they belong.

[1] - https://github.com/apt-itude/rules_pip/issues/16

Change-Id: I1065ee2fc410e52fca2be89fcbdd4cc5a4755d55
19 files changed